It is known that an industrial robot can be coordinated with a conveyor to carry out prescribed operations on work supported on a carrier as the carrier is advanced by a conveyor. In one way this is done by transporting the robot along the path of the conveyor, as disclosed in U.S. Pat. No. 3,283,918, issued Nov. 8, 1966 to George C. Devol. It has also been shown that an industrial robot whose program is appropriate to carry out prescribed operations on a work-piece at rest can be adapted to perform the same operations on a work-piece in motion by combining the program control signals with signals generated synchronously with the conveyor, as disclosed in U.S. Pat. No. 3,543,910, issued Dec. 1, 1970 to George C. Devol et al. More recently, it is suggested in application Ser. No. 132,063, the continuation of which became U.S. Pat. No. 3,818,290, filed Apr. 7, 1971 by E. V. Harper et al. that operation of an industrial program-controlled robot can be modified by signals generated by apparatus that is locked to a work-carrier moved by a conveyor past a program-controlled robot. That apparatus is relatively massive and inherently expensive. Application Ser. No. 132063 is mentioned in U.S. Pat. No. 3,665,148 which discloses a program-controlled industrial robot or manipulator to which the present invention can be applied.